Return error if adding comment on a cell which already exist comment

errors.go

@@ -193,6 +193,12 @@ func (err ErrSheetNotExist) Error() string {
 	return fmt.Sprintf("sheet %s does not exist", err.SheetName)
 }
 
+// newAddCommentError defined the error message on the comment already exist in
+// the cell.
+func newAddCommentError(cell string) error {
+	return fmt.Errorf("comment already exist on cell %s", cell)
+}
+
 // newCellNameToCoordinatesError defined the error message on converts
 // alphanumeric cell name to coordinates.
 func newCellNameToCoordinatesError(cell string, err error) error {

vml.go

@@ -108,8 +108,9 @@ func (f *File) getSheetComments(sheetFile string) string {
 // AddComment provides the method to add comments in a sheet by giving the
 // worksheet name, cell reference, and format set (such as author and text).
 // Note that the maximum author name length is 255 and the max text length is
-// 32512. For example, add a rich-text comment with a specified comments box
-// size in Sheet1!A5:
+// 32512, and each cell can only have one comment, an error will return if
+// adding comment on a cell which already exist comment. For example, add a
+// rich-text comment with a specified comments box size in Sheet1!A5:
 //
 //	err := f.AddComment("Sheet1", excelize.Comment{
 //	    Cell:   "A5",
@@ -169,10 +170,17 @@ func (f *File) DeleteComment(sheet, cell string) error {
 					cmts.CommentList.Comment[:i],
 					cmts.CommentList.Comment[i+1:]...,
 				)
+				if idx := inStrSlice(cmts.cells, cell, true); idx != -1 {
+					cmts.cells = append(
+						cmts.cells[:idx],
+						cmts.cells[idx+1:]...,
+					)
+				}
 				i--
 				continue
 			}
 			cmts.CommentList.Comment = nil
+			cmts.cells = nil
 		}
 		f.Comments[commentsXML] = cmts
 	}
@@ -272,6 +280,9 @@ func (f *File) addComment(commentsXML string, opts vmlOptions) error {
 	if cmts == nil {
 		cmts = &xlsxComments{Authors: xlsxAuthor{Author: []string{opts.Author}}}
 	}
+	if inStrSlice(cmts.cells, opts.Comment.Cell, true) != -1 {
+		return newAddCommentError(opts.Comment.Cell)
+	}
 	if inStrSlice(cmts.Authors.Author, opts.Author, true) == -1 {
 		cmts.Authors.Author = append(cmts.Authors.Author, opts.Author)
 		authorID = len(cmts.Authors.Author) - 1
@@ -320,6 +331,7 @@ func (f *File) addComment(commentsXML string, opts vmlOptions) error {
 		cmt.Text.R = append(cmt.Text.R, r)
 	}
 	cmts.CommentList.Comment = append(cmts.CommentList.Comment, cmt)
+	cmts.cells = append(cmts.cells, cmt.Ref)
 	f.Comments[commentsXML] = cmts
 	return err
 }
@@ -355,6 +367,12 @@ func (f *File) commentsReader(path string) (*xlsxComments, error) {
 			}
 		}
 	}
+	if cmts := f.Comments[path]; cmts != nil && len(cmts.cells) == 0 {
+		for idx := 0; idx < len(cmts.CommentList.Comment); idx++ {
+			cmts.cells = append(cmts.cells, cmts.CommentList.Comment[idx].Ref)
+		}
+		f.Comments[path] = cmts
+	}
 	return f.Comments[path], nil
 }
 

vml_test.go

@@ -32,6 +32,8 @@ func TestAddComment(t *testing.T) {
 	assert.NoError(t, f.AddComment("Sheet1", Comment{Cell: "A30", Author: s, Text: s, Paragraph: []RichTextRun{{Text: s}, {Text: s}}}))
 	assert.NoError(t, f.AddComment("Sheet2", Comment{Cell: "B7", Author: "Excelize", Text: s[:TotalCellChars-1], Paragraph: []RichTextRun{{Text: "Excelize: ", Font: &Font{Bold: true}}, {Text: "This is a comment."}}}))
 
+	// Test add comment on a cell which already exists a comment
+	assert.Equal(t, f.AddComment("Sheet2", Comment{Cell: "B7", Author: s, Text: s}), newAddCommentError("B7"))
 	// Test add comment on not exists worksheet
 	assert.EqualError(t, f.AddComment("SheetN", Comment{Cell: "B7", Author: "Excelize", Paragraph: []RichTextRun{{Text: "Excelize: ", Font: &Font{Bold: true}}, {Text: "This is a comment."}}}), "sheet SheetN does not exist")
 	// Test add comment on with illegal cell reference
@@ -90,15 +92,13 @@ func TestDeleteComment(t *testing.T) {
 	assert.NoError(t, f.AddComment("Sheet2", Comment{Cell: "A40", Text: "Excelize: This is a comment1."}))
 	assert.NoError(t, f.AddComment("Sheet2", Comment{Cell: "A41", Paragraph: []RichTextRun{{Text: "Excelize: ", Font: &Font{Bold: true}}, {Text: "This is a comment2."}}}))
 	assert.NoError(t, f.AddComment("Sheet2", Comment{Cell: "C41", Paragraph: []RichTextRun{{Text: "Excelize: ", Font: &Font{Bold: true}}, {Text: "This is a comment3."}}}))
-	assert.NoError(t, f.AddComment("Sheet2", Comment{Cell: "C41", Paragraph: []RichTextRun{{Text: "Excelize: ", Font: &Font{Bold: true}}, {Text: "This is a comment3-1."}}}))
 	assert.NoError(t, f.AddComment("Sheet2", Comment{Cell: "C42", Paragraph: []RichTextRun{{Text: "Excelize: ", Font: &Font{Bold: true}}, {Text: "This is a comment4."}}}))
-	assert.NoError(t, f.AddComment("Sheet2", Comment{Cell: "C41", Paragraph: []RichTextRun{{Text: "Excelize: ", Font: &Font{Bold: true}}, {Text: "This is a comment2."}}}))
 
 	assert.NoError(t, f.DeleteComment("Sheet2", "A40"))
 
 	comments, err := f.GetComments("Sheet2")
 	assert.NoError(t, err)
-	assert.Len(t, comments, 5)
+	assert.Len(t, comments, 3)
 
 	comments, err = NewFile().GetComments("Sheet1")
 	assert.NoError(t, err)

xmlComments.go

@@ -26,6 +26,7 @@ type xlsxComments struct {
 	XMLName     xml.Name        `xml:"http://schemas.openxmlformats.org/spreadsheetml/2006/main comments"`
 	Authors     xlsxAuthor      `xml:"authors"`
 	CommentList xlsxCommentList `xml:"commentList"`
+	cells       []string
 }
 
 // xlsxAuthor directly maps the author element. This element holds a string